Deposition of thin films on a substrate surface is an ubiquitous process in a variety of industries including semiconductor processing, diffusion barrier coatings and dielectrics for magnetic read/write heads. In the semiconductor industry, in particular, miniaturization seeks atomic level control of thin film deposition to produce conformal coatings on high aspect structures. One method for deposition of thin films with atomic layer control and conformal deposition is atomic layer deposition (ALD), which employs sequential, surface reactions to form layers of precise thickness controlled at the Angstrom or monolayer level. Most ALD processes are based on binary reaction sequences which deposit a binary compound film. Each of the two surface reactions occurs sequentially a thin film can be deposited with a relatively high level of control. Because the surface reactions are sequential, the two gas phase reactants are not in contact, and possible gas phase reactions that may form and deposit particles are limited.
ALD has been used to deposit metals and metal compounds on substrate surfaces. Al2O3 deposition is an example of a typical ALD process illustrating the sequential and self-limiting reactions characteristic of ALD. Al2O3 ALD conventionally uses trimethylaluminum (TMA, often referred to as reaction “A” or the “A” precursor) and H2O (often referred to as the “B” reaction or the “B” precursor). In stage A of the binary reaction, hydroxyl surface species react with vapor phase TMA to produce surface-bound AlOAl(CH3)2 and CH4 in the gas phase. This reaction is self-limited by the number of reactive sites on the surface. In stage B of the binary reaction, AlCH3 of the surface-bound compound reacts with vapor phase H2O to produce AlOH bound to the surface and CH4 in the gas phase. This reaction is self-limited by the finite number of available reactive sites on surface-bound AlOAl(CH3)2. Subsequent cycles of A and B, purging gas phase reaction products and unreacted vapor phase precursors between reactions and between reaction cycles, produces Al2O3 growth in an essentially linear fashion to obtain a targeted film thickness. Although a few processes have been developed that are effective for deposition of elemental ruthenium and other late transition metals, in general ALD processes for deposition of pure metal have not been sufficiently successful to be adopted commercially. There is a need for new deposition chemistries that are commercially viable, particularly in the area of elemental metal films, including for thin films consisting essentially of manganese. There are known methods of depositing thin manganese metal films via physical deposition methods in back end of the line processes. However, the thin metal films deposited this way have been shown to migrate to SiO2 interfaces. This forms manganese oxide, which acts as a barrier layer and prevents copper diffusion.
There is also a need for chemistries useful in the deposition of films comprising manganese nitride. Tantalum nitride (TaN) is a copper barrier at film thicknesses greater than 10 A, where the film is continuous. However, because a Ta atom is about 4 A in diameter, TaN films around 5 A thick are not continuous. For smaller nodes where thinner TaN is utilized, TaN by itself may be a discontinuous film, thus limiting the copper barrier properties of the TaN. Current methods include a Ta layer over a TaN layer, which acts as a wetting layer for copper and provides the continuity of a barrier film. For smaller nodes (less than 32 nm), however, this method leads to larger line resistance and hence is not an adequate solution. Atomic layer deposition (ALD) TaN is being used as an advanced technology with better conformality; however, the film quality of ALD TaN still needs significant improvements. MnN may be a suitable replacement for TaN, and thus new methods for deposition of MnN are sought.